nfp: flower: allow non repr netdev offload

Previously the offload functions in NFP assumed that the ingress (or
egress) netdev passed to them was an nfp repr.

Modify the driver to permit the passing of non repr netdevs as the ingress
device for an offload rule candidate. This may include devices such as
tunnels. The driver should then base its offload decision on a combination
of ingress device and egress port for a rule.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>